"I've never seen anything out of the ordinary there," said Irene Martinez, 37, who has lived in the neighborhood for four years. "I've never seen [lots of] people coming in and out of the house."

Amy Mendoza, who lives next door, said the house appeared quiet. "Everything was normal," she said.

On Friday morning, Mendoza, 18, said she saw about a dozen law enforcement officers, guns drawn, descend on the property. Outside, law enforcement officers talked to people in the rain, many barefoot, some sitting or standing on the curb. Two buses retrieved most of them, but a small group was taken away in a van, she said.

Because drop houses are usually in residential neighborhoods, they can go undetected for months or even years.

Federal agents also frequently have trouble persuading the illegal immigrants to cooperate with law enforcement. Many fear retaliation or plan to hire the smugglers again.

"Once they are sent home, they will try to come back in," Johnston said. "They'll use the same smugglers."